Wales' World Cup hopes were left in tatters as James McClean scored the only goal in Cardiff, to ensure Chris Coleman's men will not be heading to Russia - while simultaneously keeping Ireland's hopes alive.
Martin O'Neill's side secured all three points at the Cardiff City Stadium, digging it out when it mattered most and putting themselves in the play-offs.
McClean lashed in the only goal in the 57 minute after exploiting mistakes from Ashley Williams and keeper Wayne Hennessey.
With Gareth Bale in the stands due to injury, and Joe Allen subbed off in the first half with an apparent concussion, Wales struggled to create chances and never looked like breaching a resolute Irish backline.
All three points secured Ireland second spot behind Serbia in the group, and another shot at Russia 2018.
Here are five talking points from the clash in Cardiff.
1. McClean comes up trumps again for O’Neill
It was quite some time ago now that O’Neill plucked McClean seemingly from obscurity and handed him a life in the Premier League.
The boy from Derry was thrust into the limelight at Sunderland by the now Ireland boss, and has since gone on to make 55 appearances for his country.
In Cardiff, McClean bagged his 10th goal for his country, a crisp right-foot strike past Wayne Hennessey.
In 55 caps, that’s more than a decent ratio. Even more so when you consider that he didn’t bag in his first 22 games, thus bringing it down to 10 in his last 33 - all under O’Neill.
Among the three winning goals he scored during the campaign, this was his most important.
2. Coleman’s Vokes regret
Chris Coleman made one change from the weekend win over Georgia, replacing Sam Vokes with Hal Robson-Kanu.
Perhaps he’ll go to sleep tonight wishing he hadn’t.
Wales’ two best chances in the opening 70 minutes or so both fell to West Brom forward Robson-Kanu. Unfortunately, neither fell to his left foot and both were headed opportunities - very much Vokes’ domain, but less so the ex-Reading man.
Coleman rolled the dice, but didn’t get the result he wanted.
3. Hennessey and Williams’ descents continue
Wayne Hennessey has never been a favourite of Crystal Palace fans and many onlookers at Selhurst Park have long been convinced the Eagles would be better going with a different stopper.
During Everton’s dismal start to the season, Ashley Williams has been one who has borne the brunt of much Merseyside criticism.
Now, the weight of a nation may fall on the Euro 2016 heroes.
Why Wayne Hennessey felt compelled to bowl out to an under pressure centre-half in the 57th minute only he will know.
Why Williams elected to take a lackadaisical touch and bring more pressure on himself, only the ex-Swansea centre-half will know.
Combined, they played Wales under pressure, allowed Ireland to pinch possession high up the field - catching the usually organised Welsh defence at sixes and sevens - and allowed the game, and the hopes of a nation, to get away from the hosts.
4. Clark stands firm
Ciaran Clark has been impressing alongside Jamaal Lascelles for Newcastle recently, and put in an excellent defensive display in Cardiff.
There was little fuss about his performance, alongside Shane Duffy; what needed kicking was kicked, what needing heading was headed.
But the Toon defender put his body on the line - one challenge on Joe Allen in the first period was perfectly timed and bone-crunching in equal measure - and led by example in an organised defensive performance from the boys in green.
5. Without Bale, Ramsey fails to shine
In the absence of Bale, the question was whether those in red could step up and make the difference in the absence of the side's premier talent.
Given his previous in a Wales shirt and the talent he has, it was little wonder that many pinpointed Aaron Ramsey as the man who could fire them to glory.
Instead, Ramsey had a poor night. Amid poor decisions with the ball, he struggled to influence proceedings and his dismal freekick which found row Z when Wales had loaded the box waiting for his delivery, rather epitomised a poor night for the hosts.